This invention is directed to a serial printer and, in particular, to a serial printer suitable for use in hand-held portable electronic calculators or the like which includes a single printing head which carries two groups of characters alternately arranged thereon.
The printing operations performed by a serial printer which is typically used with portable electronic devices such as hand-held calculators or the like are generally performed such that a mathematical symbol, which indicates the operation performed, is printed in the first column on the printing tape and numerals are printed in the remaining columns on the printing tape. In the conventional printing method, a first type wheel which carries the symbols and a second type wheel which carries the numerals are provided such as is disclosed in Japanese Patent Laid-Open Publication No. 52-46930. In this type of printer having two type wheels, the symbols or numerals to be printed are selected by means of complex mechanisms.
In an alternative printing method, a single printing head carries both symbols and numerals on its outer circumference such as disclosed in Japanese Patent Laid-Open Publication No. 51-112617. Such a printing method is advantageous in that the construction of the printer is simplified. However, this type of printer takes a relatively long time to select the necessary symbol or numeral to be printed and a large electromagnet is generally required in order to increase the printing speed. It is, of course, desirable to have a simple, inexpensively constructed printer for use in portable electronic calculators or the like. Accordingly, a serial printer for use especially in portable electronic calculators or the like which includes a single printing head which carries both symbols and numerals and which has a simplified construction and is inexpensive to manufacture, is desired.